The present invention relates to a swash plate type variable displacement compressor.
A swash plate type variable displacement compressor is disclosed in Japanese Patent Application Publication No. 2004-218610. The compressor includes a rear housing that has therein an oil separation chamber extending in radial direction of the rear housing and an oil reserve chamber formed below the oil separation chamber in the rear end of the compressor. A hole is formed between the oil separation chamber and the oil reserve chamber, providing a fluid communication therebetween. In addition, an inlet passage is formed in the rear housing through which the oil separation chamber communicates with a discharge chamber. A discharge hole is formed in the rear housing adjacent to the oil separation chamber on the downstream side and a check valve unit, which prevents backflow of the refrigerant gas in a discharge passage, is mounted on the discharge hole. The check valve unit is provided with a pipe projecting toward the oil separation chamber, and the check valve and the pipe cooperate to form an oil separating means. A gas return passage is formed as a passage that communicates an annular port (or an intermediate pressure chamber) in a base plate of the check valve unit with the oil reserve chamber. The diameter of the gas return passage is smaller (or approximately 1 mm) than the hole between the oil separation chamber and the oil reserve chamber, and the gas return passage functions so as to allow the refrigerant in the oil reserve chamber to return to the annular port formed in the discharge passage.
In this compressor, the compressed refrigerant gas discharged from the discharged chamber is introduced into the oil separation chamber through the inlet passage. The refrigerant gas thus flowed into the oil separation chamber impinges against the outer peripheral surface of the pipe and is then flowed toward the end of the pipe while swirling around the pipe along the outer peripheral surface thereof, with the result that the oil contained in the refrigerant gas in mist form is separated from the refrigerant gas. The oil thus separated from the refrigerant gas is accumulated in the bottom of the oil separation chamber and is then flowed into the oil reserve chamber through the through hole. The oil in the oil reserve chamber is returned to a crank chamber. The refrigerant gas having the oil separated therefrom is flowed through the pipe and is then discharged to the external refrigerant circuit via a discharge pipe. Because the gas return passage is formed between the discharge passage of the refrigerant gas and the oil reserve chamber, the differential pressure ΔP between the oil separation chamber and the discharge passage causes the refrigerant gas to flow, and the oil separated from the refrigerant gas in the oil separation chamber is entrained by the refrigerant gas and flowed immediately into the oil reserve chamber through the hole.
In the compressor of the above-cited publication, however, a hole having a small diameter (approximately 1 mm) needs to be formed in the rear housing as a gas return passage that provides fluid communication between the annular port in the check valve unit and the oil reserve chamber. Machining the gas return passage of a small diameter with a drill or an end mill is extremely difficult.
The present invention, which has been made in light of the above-identified problems, is directed to providing a swash plate type variable displacement compressor that permits easy machining of a gas return passage providing fluid communication between an annular port and an oil reserve chamber.